fs/erofs: add big pcluster support

This enables EROFS big pcluster images for buildroot.

Signed-off-by: Gao Xiang <hsiangkao@aol.com>
[yann.morin.1998@free.fr: must be a multiple of 4KiB]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

fs/erofs/Config.in

@@ -11,4 +11,14 @@ config BR2_TARGET_ROOTFS_EROFS_LZ4HC
 	help
 	  Use lz4 high-compression to compress data in the filesystem.
 
+config BR2_TARGET_ROOTFS_EROFS_PCLUSTERSIZE
+	int "pcluster size"
+	default 0
+	help
+	  Specify the maximum size of physical cluster in bytes, as a
+	  multiple of 4KiB, for the big pcluster feature in order to
+	  get much better compression ratios (thus better sequential
+	  read performance for common storage devices), which has been
+	  introduced since Linux 5.13.
+
 endif # BR2_TARGET_ROOTFS_EROFS

fs/erofs/erofs.mk

@@ -10,6 +10,10 @@ ifeq ($(BR2_TARGET_ROOTFS_EROFS_LZ4HC),y)
 ROOTFS_EROFS_ARGS += -zlz4hc
 endif
 
+ifneq ($(BR2_TARGET_ROOTFS_EROFS_PCLUSTERSIZE),0)
+ROOTFS_EROFS_ARGS += -C$(strip $(BR2_TARGET_ROOTFS_EROFS_PCLUSTERSIZE))
+endif
+
 define ROOTFS_EROFS_CMD
 	$(HOST_DIR)/bin/mkfs.erofs $(ROOTFS_EROFS_ARGS) $@ $(TARGET_DIR)
 endef